The overall objective of the project is to apply the techniques of somatic cell genetics to a study of the mechanism of action of insulin and insulin-like growth factors. One aspect of this research involves an ongoing study of the mechanism by which complementation for the growth response to insulin occurs in hybrids between mouse fibroblasts and PG19 mouse melanoma cells. Previous results suggest that there is a postreceptor defect in the insulin response of the PG19 mouse melanoma cells. To further examine this possibility, several intracellular events will be examined in the PG19 melanoma cells and fibroblast x melanoma hybrid clone 100A following stimulation by insulin. Included among these events will be induction of ornithine decarboxylase and phosphorylation of ribosomal protein S6. Another aspect of this project has involved the selection of variants of hybrid clone 100A that are unable to respond to the growth-stimulatory action of insulin or MSA. The growth response of the variants to insulin and MSA in the presence and absence of other hormonal growth factors is currently being examined. Finally, experiments are being directed toward mapping the human gene for the high affinity insulin receptor using the technique of somatic cell hybridization.